bloodvette

changed my rear diff oil and used the proper weight oil in a Quaker State synthetic, but the friction modifier i bought has a GM label on it. I figured it's all the same, so I put it in. Well, I still have some rear end shuddering (but i had that before i changed the diff oil) and I read that some guys have had sucess with adding a second bottle. I only get that rear end shudder when I turn on grass slowly or when i have a load. So, i stopped in at the ford dealer becuase i happened to be going by one when i thought of it, so when i said I needa bottle of friction modifier he stopped me and he said OH you need TWO bottles. I said well i changed my diff fluid and put in one bottle but I hear a shudder. he said Oh ok and he got me a bottle. Well I mentioned I did not use a ford friction modifier for the first bottle and he said, oh your clutches are gonna deteriorate and wear out, drain it all and put all ford fluids. I said oh yea ok. and i bought the one bottle and drained enough of my diff oil to put in the FORD friction modifier and well, I haven't noticed any shuddering yet but I've only driven a few miles. I did not like the color of the oil that came out of my diff (had to drain a bit to get the other bottle in), it was pretty dirty we'll see how it goes over the next few days. I know that I may need new limited slip clutches so I thought I'd try this before doing that job myself. Any thoughts?

john

Turkey Hunter

I can definitly see a ford salesman saying that just so they will get more money.

daypass72

I replaced my diff oil a few weeks ago and used GM friction modifier also. Before the oil change I had a very slight hum on acceleration and no chatter. week after the oil change I know have chatter and the diff howl is alot louder.. So I agree do not use GM friction modifier in a ford. I will be changing the oil this weekend and using ford products. If this does not fix the problem warranty repair here I come

bloodvette

but this ford guy said I need 2 bottles. which leads me to believe that he's seen 1 bottle not do it enough times that he now tells everyone to use 2. so before you redo the whole thing consider just adding another bottle like I've done. Drove the truck again just now and no shuddering.

john